new owner 91 F250 7.3 - couple Q's

[fuzzydog]

Hi all, just bought a 91 F250 7.3 4x4 xcab. I am very competent mechanically but never had this vintage of Ford or a diesel yet. seller is a HD mechanic and very knowledgeable when questioned. I feel really good about the reliability of the truck. Just a couple of things that he just never bothered to address:

1. Seat of the pants feel tells me the speedo is off - seems to be reading way higher than actual speed. Can anyone point me to a write up of how the speedo gets it's info on these rigs?

2. Lazy tach. seems to work better as it warms up but virtually no reading upon starting cold. I know enough about diesels that there is no injection system to get a spark signal from, so can anyone give me a rundown on how the tach get's it's signal?

Thanks, and let me say great website. I can't believe the amount of info and advice in the tech forums here. Hopefully as I learn about my rig I'll be able to contribute back.

 

[kcw12]

1. There a cable and a speedo gear i believe in the 91s in 92 they went to a speed sensor on the rear end
2. theres a thing in the timing pump cover with a sensor.

 

[f350flatbed]

The tach is a Hall effect sensor. The sensor is plugged in just below the oil filler neck on the driver's side. It is ~1 inch bolt size with two wires sticking out. I had to replace mine, dealer only part, ~$50. The part number is in the parts list in the tech section.

Paul B

 

[6 Nebraska IDIs]

Actually the speed sensor in the rear is only for anti lock brakes, because all our trucks with ZF5's and E4OD's all have speedo sensors in the trans/transfer case.
That is if I remember correctly.

 

[MUDKICKR]

i have never seen a speed sensor in an e40d. i know there is a place for them but never seen a sensor, the only trucks ive seen with 5-speeds and e4ods either have a 8.8(1/2 ton) or 10.25 axles and the speed sensors are in the axles

 

[tonkadoctor]

IIRC the sensors on the tranny speedometer cable on the '91 and earlier is for the cruise control and '92 up have the sensor for the speedometer on the rear axle. Not sure about the 4x4 models.





Really ain't sure about anything with my memory anymore

 

[icanfixall]

My 89 has that funny little gizmo that looks like a generater that sits between the cable from the speedo head to the speedo gear that runs off the output shaft gear.